Past negative of な adjectives
When I first came across な adjectives, I was taught that the past negative is
[adj] + では ありません でした, e.g.
へやは しずか ではありませんでした。(The room was not quiet.)
Marugoto does things differently:
へやは しずか じゃなかったです。
Whoa! That's different, and probably a bit less formal.
So here's my question: if I use the first possibility, does this mark me as hopelessly old-fashioned? Or just very formal? Conversely, might there be people who would take exception at the second possibility?
The two meanings are exactly the same. ～ではありません is more formal than ～ではないです which is more formal than ～じゃないです。←changed to present tense, obviously. * You won't sound old-fashioned, but if you use it in the wrong situation you will seem either cold & aloof or too casual. Among good friends using the more polite forms would get you laughed at. At a work meeting (barring a convivial atmosphere), using the last one might get you cold looks.